This invention relates to machines and methods for making bulk containers and the containers made therefrom. More particularly, it is directed at a novel method and machine for making a bulk container and the container made therefrom characterized by a main body which is strengthened as compared to at least the container top or bottom by additional material layers.
Corrugated paperboard containers are often used to package and ship a variety of bulk products. Usually these containers are constructed of fiberboard, paperboard, cardboard and the like. Often, they are waxed or treated with other materials to attain desired waterproofing and other characteristics. They may take many forms and may be used for many purposes--they may consist of folding boxes or cartons, packing or shipping containers, collapsible and rigid casings and containers including transfer file cases, storage boxes, portable ward-robes, insulated containers, and other forms which are well known in the art. Examples of such containers are disclosed in U.S. Pat. Nos. 1,704,174, 2,276,363, 2,751,964, and 3,864,200.
Typically, these paperboard containers are reinforced along the edges or fold-score lines to strengthen the composite construction and preclude corner and edge damage during handling. Such protection commonly takes the form of bonding tape-like reinforcing strips about the fold lines of the blank prior to container formation. Exemplifying this type of construction are U.S. Pat. Nos. 1,425,914 and 1,600,396. Another corner reinforcement technique, disclosed in U.S. Pat. No. 1,410,622, is characterized by longitudinal folds or pleats in one of the webs of container blank. These special pleats in the zones of the fold lines of the container blank afford integral corner reinforcement and a neat appearance to the formed box.
These construction methods, while of use in strengthening the edges of the formed container, do not provide that high compressive strength needed in the packaging of heavy articles which are incapable of withstanding compressive force. Such packages tend to bulge when stacked one upon the other. Moreover, they are likely to be damaged by side panel shocks and jars.
One method to increase the lateral strength of paperboard containers comprises stiffening that corrugated paperboard employed to form the container. Such technique, disclosed in U.S. Pat. No. 3,586,564, makes use of plastic which is capable of withstanding compressive force without bending. The plastic is formed into narrow strips and dropped into the corrugated flutes at desired intervals. The resultant blank in materially stiffened in a direction parallel to the flutes. It permits a container construction which displays desired high compressive strength and lateral protection. However, this construction requires specialized apparatus for feeding and correctly positioning the narrow plastic strips on the flutes of the corrugated medium. Moreover, the use of plastic increases the cost of the formerly paper container.
Another method which enhances the compressive strength of a paperboard container and better protects its contents against lateral jars and shocks is disclosed in U.S. Pat. No. 1,550,646. There, a lining, preferably of corrugated paper or cardboard, is inserted into the container before use. This lining is characterized by double-ply top and bottom edges and a single-ply central portion. This center portion comprises a corrugated paper or cardboard core sandwiched between two liner sheets. On insertion, this construction provides a container having an air space between its outer side walls and the central portion of the liner. The formed inner air space cushions the packaged material from any lateral shocks and jars. The liner itself strengthens the compressive resistance of the box.
Although this method avoids those disadvantages inherent in the use of plastic stiffening material, it requires off-machine liner formation and resultant insertion in a formed box. Additionally, should it be desired to laminate the liner to the box, a further lamination step would be necessary. As regards the container itself, that air space separation between the container outer walls and the central portion of the liner reduces substantially the compressive and bulging resistance of the combination.
Other lining techniques are known in the prior art. These include the lamination of a single face liner-fluting-single face liner combination to the main body of the container. Such techniques require a second lamination step. Importantly, they also require an inner single face liner surface to correctly position the glue lines prior to lamination.